Genetic and Environmental Factors Influencing the Production of Select Fungal Colorants: Challenges and Opportunities in Industrial Applications

Natural colorants, mostly of plant and fungal origins, offer advantages over chemically synthetic colorants in terms of alleviating environmental pollution and promoting human health. The market value of natural colorants has been increasing significantly across the globe. Due to the ease of artificially culturing most fungi in the laboratory and in industrial settings, fungi have emerged as the organisms of choice for producing many natural colorants. Indeed, there is a wide variety of colorful fungi and a diversity in the structure and bioactivity of fungal colorants. Such broad diversities have spurred significant research efforts in fungi to search for natural alternatives to synthetic colorants. Here, we review recent research on the genetic and environmental factors influencing the production of three major types of natural fungal colorants: carotenoids, melanins, and polyketide-derived colorants. We highlight how molecular genetic studies and environmental condition manipulations are helping to overcome some of the challenges associated with value-added and large-scale productions of these colorants. We finish by discussing potential future trends, including synthetic biology approaches, in the commercial production of fungal colorants.

Extraction and optimization of Penicillium sclerotiorum strain AK-1 pigment for fabric dyeing

Recently, the demand for fungal pigments has increased due to their several benefits over synthetic dyes. Many species of fungi are known to produce pigments and a large number of fungal strains for pigment production are yet to be extensively investigated. The natural pigment from sustainable natural sources has good economic and industrial value. Many synthetic colorants used in textile and various industries have many harmful effects on the human population and environment. Pigments and coloring agents may be extracted from a wide range of fungal species. These compounds are among the natural compounds having the most significant promise for medicinal, culinary, cosmetics, and textile applications. This study attempts to isolate and optimize the fermentation conditions of Penicillium sclerotiorum strain AK-1 for pigment production. A dark yellow-colored pigment was isolated from the strain with significant extractive value and antioxidant capacity. This study also identifies that the pigment does not have any cytotoxic effect and is multicomponent. The pigment production was optimized for the parameters such as pH, temperature, carbon and nitrogen source. Fabric dyeing experiments showed significant dyeing capacity of the pigment on cotton fabrics. Accordingly, the natural dye isolated from P. sclerotiorum strain AK-1 has a high potential for industrial-scale dyeing of cotton materials.

Fungal microsclerotia development: essential prerequisites, influencing factors, and molecular mechanism

Microsclerotia (MS) consist of an outer layer of pigment parenchyma cells and an inner layer of colorless medulla cells. In nature, MS are formed as overwintering and spreading structures in phytopathogenic fungi. For biological applications, MS can be induced in artificial liquid medium. To understand the complicated structure of MS and molecular mechanism of MS development in entomopathogenic and phytopathogenic fungi, data from different studies can be integrated. In this review, the essential prerequisites, environmental cues, and internal stimulating factors for MS development are explored. Emerging knowledges about the association between transcriptional regulatory circuits and signaling pathways involved in MS development in entomopathogenic and phytopathogenic fungi is also highlighted.

Effects and Mechanism of Blue Light on Monascus in Liquid Fermentation

The effect of light on Monascus and the underlying mechanism have received a great deal of interest for the industrial application of Monascus pigments. In this study, we have examined the effects of blue light on the culture morphology, mycelium growth, pigments, and citrinin yield of Monascus in liquid-state and oscillation fermentation, and explored the mechanism at a physiological level. It was found that blue light affected the colony morphology, the composition (chitin content), and permeability of the Monascus mycelium cell wall in static liquid culture, which indicates blue light benefits pigments secreting from aerial mycelium to culture medium. In liquid oscillation fermentation, the yields of Monascus pigments in fermentation broth (darkness 1741 U/g, blue light 2206 U/g) and mycelium (darkness 2442 U/g, blue light 1900 U/g) cultured under blue light and darkness are different. The total pigments produced per gram of Monascus mycelium under blue light was also higher (4663 U/g) than that in darkness (4352 U/g). However, the production of citrinin (88 μg/g) under blue light was evidently lower than that in darkness (150 μg/g). According to the degradation of citrinin caused by blue light and hydrogen peroxide, it can be concluded that blue light could degrade citrinin and inhibit the catalase activity of Monascus mycelium, subsequently suppressing the decomposition of hydrogen peroxide, which is the active species that degrades citrinin.